JP7010558B2 - Manufacturing method of crosslinked fluororesin tube, crosslinked fluororesin tube and heat recovery article - Google Patents

Description

The present invention relates to a method for manufacturing a crosslinked fluororesin tube, a crosslinked fluororesin tube, and a heat recovery article.

Fluororesin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polytetrafluoroethylene (PTFE) are heat-resistant, slippery, and mechanical. Excellent in target strength, etc. Therefore, the use of heat-shrinkable tubes containing these fluororesins is being considered today.

However, among the above fluororesins, PFA and FEP have low melt viscosities, and therefore, when heated above the melting point, they are melt-deformed and it is difficult to maintain the desired shape. Therefore, it has been proposed today to irradiate these fluororesins with radiation at a temperature below the melting point (see Patent Document 1 and Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-135862

Hitoshi Imamura: Molding, 29 (9), 336 (2017)

However, when the method described in the above publication is used, the cross-linking of the fluororesin does not proceed or becomes insufficient, so that it is difficult to sufficiently improve the wear resistance of the molded product. That is, according to the conventional method, it is difficult to promote cross-linking of the fluororesin and enhance wear resistance while maintaining a desired shape.

The present invention has been made based on such circumstances, and a method for manufacturing a crosslinked fluororesin tube capable of manufacturing a crosslinked fluororesin tube having sufficiently high wear resistance, and a method for manufacturing a crosslinked fluororesin tube having sufficiently high wear resistance. The subject is the provision of resin tubes and heat recovery articles.

The method for producing a crosslinked fluororesin tube according to one aspect of the present invention, which has been made to solve the above problems, includes a coating step of applying a resin composition containing a fluororesin to the inner surface of a tubular body, and a coating step after the coating step. The fluororesin comprises an irradiation step of irradiating the tubular body with radiation in a low oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin, and a separation step of separating the molded body from the tubular body after the irradiation step. , Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or tetrafluoroethylene-hexafluoropropylene copolymer, wherein the tubular body contains aluminum or nickel in the surface layer on the inner surface side.

The crosslinked fluororesin tube according to another aspect of the present invention, which has been made to solve the above problems, contains a crosslinked fluororesin as a main component, and the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Alternatively, it is a tetrafluoroethylene-hexafluoropropylene copolymer and has a heat shrinkage rate of 30% or more.

The heat recovery article according to another aspect of the present invention made to solve the above problems includes the crosslinked fluororesin tube and a primer layer laminated on at least one surface of the crosslinked fluororesin tube.

The method for producing a crosslinked fluororesin tube of the present invention can produce a crosslinked fluororesin tube having sufficiently high wear resistance. Further, the crosslinked fluororesin tube and the heat recovery article of the present invention have sufficiently high wear resistance.

It is a flow figure which shows the manufacturing method of the crosslinked fluororesin tube which concerns on one Embodiment of this invention. It is a schematic perspective view which shows the coating process of the manufacturing method of the crosslinked fluororesin tube of FIG. It is a schematic perspective view which shows the irradiation process of the manufacturing method of the crosslinked fluororesin tube of FIG. It is a schematic plan view which shows the separation process of the manufacturing method of the crosslinked fluororesin tube of FIG. It is a flow chart which shows the manufacturing method of the crosslinked fluororesin tube which concerns on embodiment different from the manufacturing method of the crosslinked fluororesin tube of FIG. It is a schematic perspective view which shows the crosslinked fluororesin tube which concerns on one Embodiment of this invention. It is a schematic perspective view which shows the heat recovery article which concerns on one Embodiment of this invention.

[Explanation of Embodiment of the present invention]
First, embodiments of the present invention will be listed and described.

The method for producing a crosslinked fluororesin tube according to one aspect of the present invention includes a coating step of applying a resin composition containing a fluororesin to the inner surface of a tubular body, and a coating step of the tubular body after the coating step under a low oxygen atmosphere. The fluororesin comprises an irradiation step of irradiating radiation at a temperature equal to or higher than the melting point of the fluororesin and a separation step of separating the polymer from the tubular body after the irradiation step, and the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether. It is a copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer, and the tubular body contains aluminum or nickel in the surface layer on the inner surface side.

The method for producing the crosslinked fluororesin tube is such that a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer is coated on the inner surface of the tubular body, and the tubular body is low in weight. By irradiating the fluororesin in an oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin, the fluororesin can be sufficiently crosslinked. Further, in the method for manufacturing the crosslinked fluororesin tube, since the tubular body contains aluminum or nickel in the surface layer on the inner surface side, the fluororesin is crosslinked by cooling the fluororesin below the melting point after the crosslinking of the fluororesin. The molded body (tube body) containing the fluororesin can be separated from the tubular body. Therefore, the method for manufacturing the crosslinked fluororesin tube can manufacture a crosslinked fluororesin tube having sufficiently high wear resistance.

The upper limit of the arithmetic mean roughness Ra of the inner surface of the tubular body is preferably 100 μm. As described above, by setting the arithmetic mean roughness Ra of the inner surface of the tubular body to be equal to or less than the upper limit, the molded body can be easily separated from the tubular body in the separation step.

The melt flow rate of the fluororesin at 372 ° C. is preferably 0.5 g / 10 min or more. As described above, when the melt flow rate of the fluororesin at 372 ° C. is at least the above lower limit, the coatability of the resin composition can be improved.

The method for manufacturing the crosslinked fluororesin tube may further include a diameter-expanding step for expanding the diameter of the molded product after the separation step and a cooling step for cooling the molded product after the diameter-expanding step. As described above, the crosslinked fluororesin having a high heat shrinkage rate is further provided with the diameter-expanding step of expanding the diameter of the molded body after the separation step and the cooling step of cooling the molded body after the diameter-expanding step. The tube can be manufactured easily and reliably.

Further, the crosslinked fluororesin tube according to another aspect of the present invention contains a crosslinked fluororesin as a main component, and the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoro. It is a propylene copolymer and has a heat shrinkage rate of 30% or more.

Since the crosslinked fluororesin tube contains a crosslinked tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer as a main component, the wear resistance is sufficiently high.

The storage elastic modulus of the crosslinked fluororesin tube at 350 ° C. is preferably 1.0 × ¹⁰⁵ Pa or more. As described above, when the storage elastic modulus at 350 ° C. is at least the above lower limit, the dimensional stability of the crosslinked fluororesin tube can be sufficiently enhanced.

The limit PV value of the crosslinked fluororesin tube is preferably 200 MPa · m / min or more. As described above, when the limit PV value is at least the above lower limit, the wear resistance of the crosslinked fluororesin tube can be further enhanced.

The lower limit of the light transmittance of the crosslinked fluororesin tube is preferably 90%. Since the crosslinked fluororesin tube has excellent heat resistance, it can be used as a protective tube for lighting members such as near-ultraviolet LEDs and laser lighting elements. In this case, when the light transmittance is at least the above lower limit, it is possible to sufficiently suppress the decrease in the amount of light of the lighting member.

Further, the heat recovery article according to another aspect of the present invention includes the crosslinked fluororesin tube and a primer layer laminated on at least one surface of the crosslinked fluororesin tube.

Since the heat recovery article includes the crosslinked fluororesin tube, the wear resistance is sufficiently high.

In the present invention, the "melting point" means the melting point peak temperature measured by a differential scanning calorimeter (DSC) in accordance with JIS-K7121: 2012 "Method for measuring transition temperature of plastics". The “arithmetic mean roughness Ra” means a value measured with a cutoff value (λc) of 0.25 mm and an evaluation length (l) of 10 mm according to JIS-B0601: 2001. The "main component" refers to a component having the highest content ratio in terms of mass, for example, a component having a content of 50% by mass or more. The "heat shrinkage rate" means the rate of change from the diameter before heating based on the diameter after shrinkage heated at 350 ° C. The "light transmittance" is the transmittance of light having a wavelength of 400 nm measured in accordance with JIS-K7375: 2008 "Plastic-How to determine the total light transmittance and the total light reflectance" in a sheet body having a thickness of 1 mm. To say. "Melt flow rate" means a value measured using an extruded plastometer under the condition of a load of 21.6 kg in accordance with JIS-K-7210: 2014. The "stored elastic modulus" is a term (real number term) that constitutes a complex elastic modulus that represents the relationship between stress and strain when a viscoelastic body is subjected to a sinusoidal vibration strain, and is a viscoelastic measuring instrument (DMS). ) Refers to the value measured. The "limit PV value" is measured in accordance with JIS-K7218: 1986 "Plastic slip wear test method" under two conditions: a constant speed of 25 m / min and a constant load of 10 MPa. The lower measured value of the measured values. Specifically, a cylinder (outer diameter / inner diameter = 11.5 / 7.4) made of metal (S45C) as a mating material is placed on the test piece, and a predetermined load (surface pressure: P) is placed under dry lubrication conditions. ) Is added, the test piece is rotated at a predetermined speed (rotational speed: V), and the dynamic friction coefficient is measured by the reaction torque generated in the cylinder. At this time, it means the lower measured value (P / V value at which sudden wear occurs) obtained by keeping one of the velocity (V) and the load (P) constant and changing the other.

[Details of Embodiments of the present invention]
A preferred embodiment of the present invention will be described below with reference to the drawings.

[First Embodiment]
<Manufacturing method of crosslinked fluororesin tube>
As shown in FIG. 1, the method for producing the crosslinked fluororesin tube includes a coating step of applying a resin composition containing a fluororesin to the inner surface of a tubular body and a low oxygen atmosphere on the tubular body after the coating step. Further, the present invention includes an irradiation step of irradiating radiation at a temperature equal to or higher than the melting point of the fluororesin, and a separation step of separating the molded body from the tubular body after the irradiation step. The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Further, the tubular body contains aluminum or nickel in the surface layer on the inner surface side. The "surface layer on the inner surface side" means a layer exposed on the outermost surface on the inner surface side.

The method for manufacturing the crosslinked fluororesin tube is such that the fluororesin (PFA or FEP) is coated on the inner surface of the tubular body, and the tubular body is subjected to a low oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin. By irradiating with radiation, the fluororesin can be sufficiently crosslinked. The method for manufacturing the crosslinked fluororesin tube is to irradiate the fluororesin from the outer surface side of the tubular body while heating the fluororesin to a temperature equal to or higher than the melting point, so that the radiation transmitted through the tubular body is emitted from the fluororesin. Is to irradiate. In the method for producing the crosslinked fluororesin tube, since the fluororesin is irradiated with radiation while the outer surface side of the resin composition coated in the coating step is supported by the tubular body, the entire resin composition has a tube shape. The fluororesin can be sufficiently crosslinked while maintaining the above. Further, in the method for manufacturing the crosslinked fluororesin tube, since the tubular body contains aluminum or nickel in the surface layer on the inner surface side, the crosslinked fluororesin is obtained by cooling the fluororesin to below the melting point after cross-linking. The contained molded body (tube body) can be separated from the tubular body. That is, since the linear expansion coefficient of the fluororesin is larger than the linear expansion coefficient of the material for forming the tubular body, the fluororesin is cooled below the melting point after crosslinking to heat shrink the tubular body and the molded body. The molded body can be easily separated from the tubular body by utilizing the difference in coefficient. Therefore, the method for manufacturing the crosslinked fluororesin tube can manufacture a crosslinked fluororesin tube having sufficiently high wear resistance.

(Applying process)
As shown in FIG. 2, in the coating step, a resin composition containing PFA or FEP is coated on the inner surface of the tubular body 1. In the coating step, it is preferable to coat the inner surface of the tubular body 1 with a substantially uniform thickness of the resin composition. As a result, the resin composition is formed on a tubular coating film 2 having an outer diameter equal to the inner diameter of the tubular body 1.

<Cylindrical body>
The tubular body 1 contains a metal as a main component. Examples of the metal include aluminum, stainless steel and the like. The shape of the tubular body 1 is not particularly limited as long as it is tubular, and examples thereof include a cylindrical shape and a polygonal tubular shape. Further, as the tubular body 1, it is also possible to use a cylindrical body 1 having a diameter that changes along the axial direction or a bottomed cylindrical body.

The tubular body 1 is preferably formed to have a substantially uniform thickness so that the amount of radiation transmitted is equal. The average thickness of the tubular body 1 is not particularly limited as long as it can appropriately transmit radiation while maintaining the required intensity, and can be, for example, 100 μm or more and 1000 μm or less.

As described above, the tubular body 1 contains aluminum or nickel in the surface layer on the inner surface side. The tubular body 1 preferably contains aluminum or nickel on the entire surface layer on the inner surface side. It is considered that the tubular body 1 contains aluminum or nickel in the surface layer on the inner surface side, so that the molded body obtained by cross-linking the fluororesin can be easily separated. Examples of the surface layer on the inner surface side of the tubular body 1 containing aluminum include a configuration in which the entire tubular body 1 is made of aluminum, and a configuration in which an aluminum layer is formed on the inner surface of another metal body such as stainless steel. Can be mentioned. Further, as an example in which the surface layer on the inner surface side of the tubular body 1 contains nickel, for example, the entire tubular body 1 is made of nickel, or the inner surface of another metal body such as stainless steel is subjected to alkaline electropolishing treatment. Can be mentioned. It is considered that nickel is concentrated on the surface layer of the main body by subjecting the inner surface of the main body to an alkaline electrolytic polishing treatment, and the separability from the molded body is enhanced.

The upper limit of the arithmetic mean roughness Ra of the inner surface of the tubular body 1 is preferably 100 μm, more preferably 50 μm, and even more preferably 20 μm. If the arithmetic mean roughness Ra exceeds the upper limit, it may not be easy to separate the molded body from the tubular body 1 in the separation step described later. On the other hand, the smaller the arithmetic mean roughness Ra of the inner surface of the tubular body 1, the more preferable, and the lower limit thereof is not particularly limited and may be 0 μm.

<Resin composition>
The resin composition may contain only one of PFA and FEP as the fluororesin, or may contain both PFA and FEP. Further, the fluororesin may contain a polymerization unit derived from another copolymerizable monomer as long as the effect of the present invention is not impaired. The upper limit of the content ratio of the polymerization unit derived from the other copolymerizable monomer is, for example, 3 mol% with respect to all the polymerization units constituting the fluororesin.

The lower limit of the melt flow rate (MFR) of the fluororesin at 372 ° C. is preferably 0.5 g / 10 min, more preferably 10 g / 10 min, and even more preferably 15 g / 10 min. If the MFR does not reach the lower limit, the coatability of the resin composition may be insufficient. The upper limit of the MFR is not particularly limited, but may be, for example, 35 g / 10 min from the viewpoint of easily and surely forming a coating film on the inner surface of the tubular body 1.

The resin composition may contain a dispersant for uniformly dispersing the fluororesin. Examples of the dispersant include a mixed solution of water and an emulsifier, a mixed solution of water and alcohol, a mixed solution of water and acetone, a mixed solution of water, alcohol and acetone, and the like.

The lower limit of the content of the fluororesin in the resin composition excluding the dispersant is preferably 60% by mass, more preferably 85% by mass, still more preferably 98% by mass. Further, the content is particularly preferably 100% by mass. If the content does not reach the lower limit, heat resistance, slipperiness, mechanical strength and the like may be insufficient.

The resin composition may contain other fluororesins, other optional components, and the like as long as the effects of the present invention are not impaired. Examples of the other fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and chlorotrifluoroethylene. -Ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), fluoroolefin-vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer and the like can be mentioned. In addition, examples of the optional component include a colorant, a conductive material, a heat radiating material, a fluorescent agent, a reflective agent, and the like.

<Applying method>
As a coating method in the coating step, for example, a resin composition (dispersion) in which a cylindrical body 1 is arranged so that the axial direction is in the vertical direction and the fluororesin powder is uniformly dispersed in the dispersant. A method of hanging the tubular body 1 from above, and a method of immersing the tubular body 1 in the dispersion.

(Irradiation process)
In the irradiation step, as shown in FIG. 3, the outer surface of the tubular body 1 is formed in a low oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin, with the coating film 2 formed on the inner surface of the tubular body 1. Irradiate from the side. As a result, in the irradiation step, the dispersion medium is evaporated and the fluororesin is crosslinked. As a result, a tubular molded body obtained by curing the fluororesin tree is obtained. When the resin composition contains both PFA and FEP, it is preferable to irradiate the radiation at a temperature equal to or higher than the melting point of the higher melting point (PFA) of PFA and FEP in the irradiation step.

The specific radiation irradiation temperature in the irradiation step is 310 ° C. or higher when the fluororesin is PFA (melting point: 304 ° C. or higher and 310 ° C. or lower), and the fluororesin is FEP (melting point: 270 ° C.). In some cases, it is above 270 ° C. As the lower limit of the irradiation temperature of radiation in the irradiation step, a temperature 5 ° C. higher than the melting point is preferable. On the other hand, as the upper limit of the irradiation temperature, a temperature 50 ° C. higher than the melting point is preferable, and a temperature 20 ° C. higher than the melting point is more preferable. By irradiating with radiation at the above temperature, it is possible to promote cross-linking between molecules while suppressing the cleavage of the main chain of the fluororesin.

As the upper limit of the oxygen concentration in the irradiation step, 100 volume ppm is preferable, 10 volume ppm is more preferable, and 5 volume ppm is further preferable. If the oxygen concentration exceeds the upper limit, the fluororesin may be decomposed.

Examples of the radiation include ionizing radiation such as γ-rays, electron beams, X-rays, neutron rays, and high-energy ion rays. The lower limit of the irradiation dose of ionizing radiation is preferably 10 kGy, more preferably 70 kGy, and even more preferably 260 kGy. If the irradiation dose is smaller than the lower limit, the cross-linking reaction of the fluororesin may not proceed sufficiently. On the other hand, as the upper limit of the irradiation dose, for example, 2000 kGy is preferable, 1200 kGy is more preferable, and 400 kGy is further preferable, from the viewpoint of preventing the irradiation amount from becoming unnecessarily large.

(Separation process)
In the separation step, as shown in FIG. 4, the molded body 3 formed in the irradiation step is separated from the tubular body 1. In the separation step, the temperature heated above the melting point of the fluororesin by the irradiation step is cooled to below the melting point of the fluororesin, and the linear expansion coefficient of the fluororesin and the linear expansion coefficient of the formed metal of the tubular body 1 are obtained. The molded body 3 is separated from the tubular body 1 by utilizing the difference between the above. Specifically, in the separation step, the temperature heated above the melting point of the fluororesin in the irradiation step is cooled to less than the melting point of the fluororesin, so that the diameter of the molded body 3 becomes the diameter of the tubular body 1. The diameter is relatively reduced, and the molded body 3 is separated from the tubular body 1.

The cooling temperature in the separation step can be, for example, 10 ° C. or higher and 30 ° C. or lower.

In the separation step, it is also possible to adopt a method of separating the molded body 3 by dissolving or decomposing the base material with a chemical or the like.

[Second Embodiment]
The method for producing the crosslinked fluororesin tube of FIG. 5 is a coating step of applying a resin composition containing a fluororesin to the inner surface of a tubular body, and a method of applying the fluororesin to the tubular body after the coating step under a low oxygen atmosphere. An irradiation step of irradiating radiation at a temperature equal to or higher than the melting point, a separation step of separating the molded body from the tubular body after the irradiation step, a diameter-expanding step of expanding the diameter of the molded body after the separation step, and the expansion of the diameter. It is provided with a cooling step for cooling the molded product after the diameter step. In the method for producing the crosslinked fluororesin tube, the fluororesin is PFA or FEP, and the tubular body contains aluminum or nickel in the surface layer on the inner surface side. The coating step, irradiation step, and separation step of the method for manufacturing the crosslinked fluororesin tube are the same as the coating step, irradiation step, and separation step of the method for manufacturing the crosslinked fluororesin tube of FIG. That is, the method for manufacturing the crosslinked fluororesin tube includes a diameter expansion step and a cooling step as a post-step of the separation step of FIG. Therefore, in the following, only the diameter expansion process and the cooling process will be described.

Since the method for manufacturing the crosslinked fluororesin tube further includes a diameter expansion step and a cooling step after the separation step, it is possible to easily and surely manufacture a crosslinked fluororesin tube having a high heat shrinkage rate.

(Diameter expansion process)
The diameter expansion step can be performed, for example, by using a known substantially cylindrical sizing tube (not shown) having an internal space through which the molded body 3 separated in the separation step passes. In the diameter expansion step, for example, gas is supplied into the molded body 3 passing through the sizing tube while reducing the pressure in the internal space. Thereby, in the diameter expansion step, the outer diameter of the molded body 3 can be expanded to the inner diameter of the sizing pipe.

(Cooling process)
In the cooling step, the molded body 3 whose diameter has been expanded in the diameter expanding step is cooled and fixed. As a result, the molded body 3 after cooling and fixing is configured as the crosslinked fluororesin tube 11 of FIG. The diameter of the crosslinked fluororesin tube 11 after cooling and fixing by the cooling step is substantially equal to the diameter after the diameter expansion by the diameter expanding step. Examples of the cooling source in the cooling step include water, cold air, and a refrigerant.

<Cross-linked fluororesin tube>
The crosslinked fluororesin tube 11 of FIG. 6 is obtained by the method for manufacturing the crosslinked fluororesin tube. The crosslinked fluororesin tube 11 contains a crosslinked fluororesin as a main component, the fluororesin is PFA or FEP, and the heat shrinkage rate is 30% or more.

Since the crosslinked fluororesin tube 11 contains crosslinked PFA or FEP as a main component, the wear resistance is sufficiently high.

Further, since the crosslinked fluororesin tube 11 is sufficiently crosslinked with the fluororesin, the diameter can be sufficiently expanded in the diameter expansion step, whereby the heat shrinkage rate can be 30% or more. .. When the heat shrinkage rate of the crosslinked fluororesin tube 11 is at least the above lower limit, the crosslinked fluororesin tube 11 can easily shrink into a deformed shape, and can appropriately cover members having various shapes.

The lower limit of the heat shrinkage of the crosslinked fluororesin tube 11 is preferably 50%, more preferably 95%. When the heat shrinkage rate is at least the lower limit, it becomes easier to shrink into a deformed shape. The upper limit of the heat shrinkage rate is not particularly limited, but may be, for example, 300% from the viewpoint of easily and surely performing the above-mentioned diameter expansion step.

The lower limit of the storage elastic modulus of the crosslinked fluororesin tube 11 at 350 ° C. is preferably 1.0 × 10 ⁵ Pa, more preferably 1.2 × 10 ⁵ Pa. If the storage elastic modulus does not reach the lower limit, the dimensional stability of the crosslinked fluororesin tube 11 may be insufficient. On the other hand, the upper limit of the storage elastic modulus of the crosslinked fluororesin tube 11 at 350 ° C. is not particularly limited, but may be, for example, 1.0 × 10 ⁹ Pa.

The lower limit of the limit PV value of the crosslinked fluororesin tube 11 is preferably 200 MPa · m / min, more preferably 500 MPa · m / min, and even more preferably 800 MPa · m / min. If the limit PV value does not reach the lower limit, the wear resistance of the crosslinked fluororesin tube 11 may be insufficient. On the other hand, the upper limit of the limit PV value of the crosslinked fluororesin tube 11 is not particularly limited, but may be, for example, 1000 MPa · m / min.

The lower limit of the light transmittance of the crosslinked fluororesin tube 11 is preferably 90%, more preferably 95%. In the crosslinked fluororesin tube 11, the crystals of the fluororesin are subdivided by irradiation with radiation in the irradiation step, whereby the light transmittance can be increased. Further, since the crosslinked fluororesin tube 11 is excellent in heat resistance, it can be used as a protective tube for a lighting member such as a near-ultraviolet LED or a laser lighting element. In this case, if the light transmittance does not reach the lower limit, the amount of light of the lighting member may be insufficient. The upper limit of the light transmittance is not particularly limited and may be, for example, 100%.

[Third Embodiment]
<Heat recovery goods>
The heat recovery article 21 of FIG. 7 includes a crosslinked fluororesin tube 11 of FIG. 6 and a primer layer 22 laminated on at least one surface of the crosslinked fluororesin tube 11. In the heat recovery article 21, a primer layer 22 is laminated on the outer peripheral surface of the crosslinked fluororesin tube 11. The primer layer 22 is preferably laminated on the entire outer peripheral surface of the crosslinked fluororesin tube 11. The heat recovery article 21 is a two-layer body of a crosslinked fluororesin tube 11 and a primer layer 22.

Since the heat recovery article 21 includes the crosslinked fluororesin tube 11, the wear resistance is sufficiently high.

(Primer layer)
The primer layer 22 is disposed between the crosslinked fluororesin tube 11 and the article to be adhered (not shown), and enhances waterproofness and adhesion between the crosslinked fluororesin tube 11 and the article to be adhered. That is, the primer layer 22 is an adhesive layer that adheres the crosslinked fluororesin tube 11 and the article to be adhered. Examples of the main component of the primer layer 22 include synthetic resins such as PFA, polyether sulfone (PES), and polyamide. The synthetic resin may be crosslinked by irradiation with ionizing radiation or the like. Further, the primer layer 22 may contain additives such as a viscosity property improving agent, a deterioration inhibitor, a flame retardant, a lubricant, a colorant, a heat stabilizer, an ultraviolet absorber, and a pressure-sensitive adhesive.

Since the heat recovery article 21 includes the primer layer 22, the crosslinked fluororesin tube 11 containing the crosslinked fluororesin as a main component can be easily and surely adhered to the object to be adhered, such as metal or rubber. Can be done. More specifically, according to the conventional method, it is necessary to crosslink the fluororesin after coating the crosslinked fluororesin tube on the object to be adhered, so that the article to be adhered cannot withstand the heating temperature, which is desirable. It was difficult to obtain the adherend of. On the other hand, since the fluororesin is preliminarily crosslinked in the heat recovery article 21, the crosslinked fluororesin tube 11 is easily and surely coated on the object to be adhered while suppressing deterioration of the quality of the article to be adhered. You can wear it. In particular, in the heat recovery article 21, the primer layer 22 is laminated on the outer peripheral surface of the crosslinked fluororesin tube 11, so that the crosslinked fluororesin tube 11 is easily and surely laminated on the inner peripheral surface of the article to be adhered. Can be done.

<Manufacturing method>
The method for producing the heat recovery article 21 includes a laminating step of laminating the primer layer 22 on the crosslinked fluororesin tube 11.

The laminating step is a coating step of applying a primer layer forming composition for forming a primer layer 22 on at least one surface of a crosslinked fluororesin tube 11, and firing of the primer layer forming composition after the coating step. It has a firing step.

The method for manufacturing the heat recovery article can easily and surely manufacture the heat recovery article 21 having sufficiently high wear resistance.

[Other embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. To.

For example, the specific procedure of the diameter expansion step and the cooling step is not particularly limited. Further, the method for manufacturing the crosslinked fluororesin tube may include a winding step of winding the molded product after cooling by the cooling step.

In the heat recovery article, the primer layer does not necessarily have to be laminated on the outer peripheral surface of the crosslinked fluororesin tube, and may be laminated on the inner peripheral surface of the crosslinked fluororesin tube. Further, the primer layer may be laminated on both sides of the crosslinked fluororesin tube.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[Example]
[No. 1]
As the above-mentioned coating step, powder-like PFA (Mitsui Dupont Fluoro) is applied to the inner surface of an aluminum foil (1050) pipe having an average thickness of 200 μm, an average inner diameter of 30 mm, and a maximum height roughness Rz of 1 μm specified in JIS B0601: 2013 on the inner surface. "MP102" manufactured by Chemical Co., Ltd.) was coated with electrostatic powder. The melting point of the PFA was 310 ° C. and the MFR at 372 ° C. was 20 g / 10 min. Next, after firing the PFA at 350 ° C. for 20 minutes, as the above-mentioned irradiation step, the PFA is heated to 330 ° C. in a low oxygen atmosphere having an oxygen concentration of 5 volume ppm or less, and an electron beam accelerator manufactured by NHV Corporation is used. The electron beam was irradiated from the outer surface side of the aluminum pipe. The irradiation conditions were an acceleration voltage of 1160 kV and an irradiation amount of 300 kGy. Subsequently, as the above-mentioned separation step, the mixture was cooled to 25 ° C., and the tubular molded body formed on the inner surface of the tubular body was separated by utilizing the difference in the linear expansion coefficients of aluminum and PFA. As a result, a crosslinked fluororesin tube containing a crosslinked PFA having an average thickness of 180 μm and an inner diameter of 30 mm as a main component was produced.

[Comparison example]
[No. 2]
No. except that the above irradiation step was not performed. A crosslinked fluororesin tube was manufactured in the same manner as in 1.

[No. 3]
No. except that the heating temperature in the above irradiation step was set to 200 ° C. and the irradiation amount of the electron beam was set to 50 kGy. A crosslinked fluororesin tube was manufactured in the same manner as in 1.

<Quality of cross-linked fluororesin tube>
(Storage modulus)
No. 1 to No. A test piece was prepared by cutting the crosslinked fluororesin tube of No. 3 into a rectangular shape having a length of 20 mm and a width of 10 mm. These test pieces were measured using a viscoelasticity measuring instrument (DMS) (“DVA-200” manufactured by IT Measurement Control Co., Ltd.) in a nitrogen atmosphere in a measurement temperature range of 25 ° C. to 400 ° C. and a heating rate of 10 ° C./min. The measurement was performed with a strain amplitude of 5 μm, a measurement frequency of 1 Hz, a minimum tension of 9.8 mN, and an initial force amplitude of 29.4 mN. Table 1 shows the measurement results of the storage elastic modulus at 350 ° C.

(Limited PV value)
No. 1 to No. A test piece was cut out from the crosslinked fluororesin tube of No. 3, and the test piece was heat-sealed at 330 ° C. to a 2 mm-thick aluminum plate (3003) in which uncrosslinked PFA was laminated to a thickness of 50 μm, and then thrust wear. It was set in a testing machine and the limit PV value was calculated. As the mating material, a cylinder having a material of S45C and a ring size (outer diameter / inner diameter) of Φ11.5 / Φ7.4 was used. The measurement results of the limit PV value are shown in Table 1.

(Heat shrinkage rate)
No. The crosslinked fluororesin tube of No. 1 is fixed in the expanded state by applying an internal pressure of 0.1 MPa at a temperature of 320 ° C., expanding the inner diameter to 60 mm (diameter expansion step), and cooling with water immediately after the diameter expansion (cooling step). did. When the expanded crosslinked fluororesin tube was heated at 350 ° C., the inner diameter shrank to 31 mm.

(Heat recovery goods)
The crosslinked fluororesin tube after the cooling step described above was heated at 350 ° C. and coated on the outer peripheral surface of an aluminum pipe having an inner diameter of 30 mm. A composition for forming a primer layer containing PES and PFA at a ratio of 1: 1 was applied to the outer peripheral surface of the crosslinked fluororesin tube after coating, and then calcined at 330 ° C. for 20 minutes to obtain the outer periphery of the crosslinked fluororesin tube. A heat recovery article in which a primer layer was laminated on the surface was manufactured. In this heat recovery article, the crosslinked fluororesin tube and the primer layer were heat-sealed, and the peel strength between them at 25 ° C. was 10 N / cm.

(Applied body)
The heat recovery article was pulled out from an aluminum pipe, arranged on the inner peripheral surface of a pipe made of SUS304 having an inner diameter of 40 mm, and expanded by adding air at 350 ° C. to the inner surface side. As a result, an adherend was obtained in which the primer layer and the pipe made of SUS304 were adhered to each other, and the pipe and the crosslinked fluororesin tube were adhered to each other via the primer layer.

[Evaluation results]
As shown in Table 1, No. Since the fluororesin is sufficiently crosslinked in the crosslinked fluororesin tube of No. 1, the limit PV value and the storage elastic modulus at 350 ° C. are No. 1. 2 and No. It is larger than the crosslinked fluororesin tube of 3. From this, No. It can be seen that the crosslinked fluororesin tube of No. 1 has excellent wear resistance and dimensional stability.

In addition, as described above, No. The crosslinked fluororesin tube of 1 has a high heat shrinkage rate. Furthermore, No. In the heat recovery article using the crosslinked fluororesin tube of No. 1, an adherend having high peel strength between the crosslinked fluororesin tube and the primer layers and excellent adhesion is obtained.

As described above, the method for manufacturing a crosslinked fluororesin tube according to the present invention can manufacture a crosslinked fluororesin tube having sufficiently high wear resistance, and thus is preferably used for cross-linking OA equipment, lighting members, and the like. Suitable as a method for manufacturing fluororesin tubes.

1 Cylindrical body 2 Coating film 3 Molded body 11 Cross-linked fluororesin tube 21 Heat recovery article 22 Primer layer

Claims (7)

A coating process in which a resin composition containing a fluororesin is applied to the inner surface of a cylindrical body, and
An irradiation step of irradiating the tubular body after the coating step with radiation in a low oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin,
A separation step of separating the molded body from the tubular body after the irradiation step is provided.
The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer.
A method for manufacturing a crosslinked fluororesin tube in which the tubular body contains aluminum or nickel in the surface layer on the inner surface side. The method for producing a crosslinked fluororesin tube according to claim 1, wherein the arithmetic mean roughness Ra of the inner surface of the tubular body is 100 μm or less. The method for producing a crosslinked fluororesin tube according to claim 1 or 2, wherein the melt flow rate of the fluororesin at 372 ° C. is 0.5 g / 10 min or more. A diameter-expanding step for expanding the diameter of the molded body after the separation step,
The method for manufacturing a crosslinked fluororesin tube according to claim 1, claim 2 or claim 3, further comprising a cooling step for cooling the molded body after the diameter expansion step. The main component is cross-linked fluororesin.
The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer.
The heat shrinkage rate is 30% or more ,
A crosslinked fluororesin tube having a storage elastic modulus at 350 ° C. of 1.0 × ¹⁰⁵ Pa or more and a limit PV value of 200 MPa · m / min or more . The crosslinked fluororesin tube according to claim 5, which has a light transmittance of 90% or more. A heat recovery article comprising the crosslinked fluororesin tube according to claim 5 or 6 , and a primer layer laminated on at least one surface of the crosslinked fluororesin tube.

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